Continuous-flow heater, more particularly for hot-water circulation heating systems



May 14, 1968 KEPPEL ET AL 3,382,717

-FLOW HEATER, MORE PARTICULAR FQR HOT-WATER CONT INUOUS C IRCULAT ION HEATING SYSTEMS 2 Sheets-Sheet '1 Filed Jan. 20, 1966 I v INVENTORS May 14, 1968 KEPPEL ET AL 3,382,717

CONTINUOUS-FLOW HEATER, 'MORE PARTICULAR FOR HOT-WATER CIRCULATION HEATING SYSTEMS Filed Jan. 20, 1966 2 Sheets-Sheet 2 INVENTORAS': 8M 14% AIM mg BY M,M \WIVW;

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United States Patent CONTINUOUS-FLOW HEATER, MORE PAR- TICULARLY FOR HOT-WATER CIRCU- LATION HEATING SYSTEMS Ernst Keppel and Hans Piitz, Remscheid, Germany, assignors to Job. Vaillant KG, Remscheid, Germany Filed Jan. 20, 1966, Ser. No. 521,862 Claims priority, application Germany, Mar. 27, 1965, V 28,163; June 12, 1965, V 28,665 9 Claims. (Cl. 73-3628) ABSTRACT OF THE DISCLOSURE A hot water heating system has a fin block through which water flows and externally of which the hot gases of combustion flow. A well for a temperature sensor is provided with metallic walls. These walls may be an integral part of the water carrying fin tube of the fin block or they may be a composite of the fin tube and an external or internal sleeve soldered to the fin tube in a manner such that the solder forms a part of the metal heat conducting path between the well and the exterior thereof. In any event, a first portion of the external area of the metallic member defining the well is exposed to the water and a second portion of the external area is exposed to the gases, and they are formed so that direct metal heat conduction paths exist between said areas and said well, the second portion of the external area being a major part of the exposed area of the metal. The heat sensor is slightly smaller than the well and is urged against that part of the metal defining the well which is most closely adjacent said first portion.

Background of the invention The present invention relates to a continuous-flow heater, more particularly for hot-water circulation heating systems. In continuous-flow heaters it is known to provide a heat sensor of a thermostat, for instance, of a liquid thermostat, which is in heat-conducting connection with a flow tube of a fin block disposed in the heating gas current. In prior art arrangements of this type water flows around the heat sensor internally of the flow tube, and by webs constituting heat bridges the sensor is connected with the flow tube. Further, a heat sensor is known which bears on the top of a flow tube in linear engagement therewith and which together with the flow tube, extends through the recesses of the fins of the fin block. The prior art heat sensing arrangements are not suflicient to effectively protect the heat exchanger designed as fin block against overheating. If the heat sensor with web-type heat bridges to the flow tube is arranged in the Water stream, it will primarily assume the water temperature and, for instance, in the case of water deficiency or vapor formation will not respond in time to an increase in the temperature of the flow tube, since the heat transfer via web-type heat bridges is too small. If, however, the heat sensor is arranged externally of the flow tube in the fin block, without the water temperature being capable of influencing the sensor markedly, the heat sensor in normal state of operation will be at fin temperature. The latter, however, upon temporary switch-off of the heating capacity or a reduction of the heating capacity will decrease to a greater extent than will the water temperature so that the heat sensor is sub jected to relatively large temperature variations, where by its response time is extended. If the full heating capacity is then switched on again, it will take a certain time until the fin temperature and that of the heat sensor will again have reached their operating level. During this time, also the water which had remained hotter, picks 3,382,717 Patented May 14, 1968 up heat and will thereby obtain a considerable excess temperature which may lead to undesired development of excess pressure in closed central heating systems.

It is therefore the object of the present invention in a continuous-flow heater to provide a heat sensing arrangement for protection of the fin block and of the water against overheating, wherein the heat sensor detects an increase in the temperature of the fin block with as little delay as possible and upon temporary switch-oflf or reduction of the heating capacity is not only subjected to the large and relatively quick temperature variations of the outer parts of the fin block having only a low heat capacity, but is at the same time influenced also by the water temperature.

According to the present invention this object is being attained by providing that the heat sensor is tightly enclosed by a wall preventing a Water contact of the heat sensor, but which for the total length thereof and for the major part of its circumference has direct heat-conducting connection with the wall of the water carrying flow tube. With such an arrangement the heat sensor may be removed from the fin block in dry state, without the flow channel having to be opened; that the heat sensor is influenced both by the water temperature and by the temperature of the fin block, and is therefore suited as safety device to control a thermostat disposed between the heat exchanger and the radiator of the heating system; and that replaces a thermostat only responding to fin block excess temperature. In the arrangement as described the operating temperature of the heat sensor is above the temperature of the water under normal operating conditons so that the increases in the water temperature caused by after-heat will not yet cause the thermostat to respond.

However, it has shown that the temperature which the sleeve wall assumes under these influences, is not uniform, but that there will occur a temperature drop in the sleeve wall towards the side which faces the water. Since it is impossible for technical reasons in the manufacture to attain an overall uniform engagement of the inserted heat sensor with the sleeve wall, the temperature assumed by the heat sensor will depend on the incidental position which the heat sensor is in at that moment internally of the sleeve. To eliminate these difliculties, provision is suitably made that the heat sensor is caused to engage internally that portion of the wall the outer side of which faces the water carried through the flow tube. Thereby the water temperature has optimum influence on the heat sensor, while the influence of the fin block temperature, though being weakened, still remains sufliciently great to cause the heat sensor in the case of dry-burning to switch olf the heating capacity.

The invention may be designed in various manners. The heat sensor may be inserted in a sleeve closed at one end thereof, arranged in the flow tube and soldered to the wall thereof, on which there is supported a heatcondueting metal sheet covering soldered to the wall of the flow tube. The metal sheet covering may be a fluid guiding plate mounted perpendicularly in the flow tube, the bottom portions of which are embossed to correspond to the rounding of the sleeve and support on the sleeve. A fluid guiding sheet that is carried through the water stream and is in heat-conducting engagement with the walls of the flow tube, serves for better dis tribution of temperature within the water stream. In the manner as herein described it may at the same time be used to form the metal sheet covering.

The arrangement may also be provided such that the heat sensor is inserted in a sleeve which is arranged externally of a flow tube and soldered thereto that is formed with a longitudinal embossment adapted to the sleeve rounding, so that the flow tube and the sleeve constitute a common body fitting within the recesses of the fins. Finally, the flow tube below a water carrying channel may be formed with a further channel separated therefrom by an intermediate surface, having inserted therein the heat sensor.

Description of the drawings FIG. 1 illustrates a longitudinal section through a fin tube with soldered-in thermostat sleeve.

FIG. 2 is a section at line A-B of FIG. 1 through the lower portion of the fin tube with the sleeve to an enlarged scale as compared with FIG. 1.

FIG. 3 illustrates a circular fin tube with soldered in tube sleeve and a metal sheet covering soldered to both main parts.

FIG. 4 illustrates a fin tube in section comprising a special channel intended for the heat sensor.

FIG. 5 illustrates a fin tube in section comprising an externally abutting sleeve for the heat sensor.

Reference numeral 1 designates a fin tube of a fin block, oval in cross-section, having fins 2 mounted thereon in known manner. The fin block closes off the top of the heating compartment H (shown only in part) of a gas-heated continuous-flow heater. The water to be heated flows through the fin tube 1 in the direction of the arrow. Several of these fin tubes are arranged in juxtaposed relation to each other on the fin block and are connected with each other by bends 3. At the lowermost point of the fin tube 1 a metal sleeve 4 is soldered. Sleeve 4 is being closed at one end thereof. Further, the metal sleeve 4 is in heat heat-conducting connection with a web plate 5. To achieve this, the lower end of this web plate 5 is cut at intervals and the bent-off tongues 5', 5" from the center abut the sleeve 4, alternating to the right and left. The web plate 5 is inserted in the fin tube 1 and at the uppermost part of the fin tube 1 is in heat-conducting engagement therewith. Sleeve 4 defines a well 8 to receive sensor 6.

Prior to insertion of the sleeve, the latter is pressed in at the underside thereof so that a few bosses 4 will be produced. A cylindrical heat sensor 6 which is inserted into the sleeve 4, bears on the bosses 4' of the sleeve 4 which causes the rounded top thereof to come into heat-conducting engagement with the upper portion of the sleeve wall, facing the water.

Therefore, a direct heat transmission from the water to the heat sensor 6 is ensured, while the heat transmission from the fin tube 1 and the lower portion of sleeve 4, respectively, to the heat sensor is only possible through an air gap 7.

In the embodied form according to FIG. 3 the sleeve 13 soldered to the lowermost point of a circular flow tube 10 is covered by a metal sheet covering 16 the ends 16' of which abut the wall of the flow tube 10. With the soldering thereof, here too, such a large metallic cross-section is available for the heat transfer that the sleeve 13, in operation of the apparatus, assumes a temperature being above the temperature of the water under normal operating conditions. Sleeve 13 forms a well 14 to receive the heat sensor 6 (not shown in FIG. 3).

According to FIG. 4 the cross-section of a flow tube 17 is divided into two channels 17, 17". The upper channel 17 is the Water carrying flow channel while the lower channel 17" forms a well to accommodate the heat sensor 6. Of course, one end of the channel 17" is closed.

It is also possible, as is illustrated in FIG. 5, to form the flow tube 18 such that the tube sleeve 13 positively engages the flow tube 18 provided with a longitudinal embossment 18'. After soldering of the two parts 18, 13 together and to the fins 2 a good heat transfer is ensured in the meaning of the invention. The profile of the dual body formed in such manner fits in the customary recess of the fins 2. Also the heat sensor 6 will be inserted into sleeve 13 and channel 17" so that it internally abuts at the top thereof, which may be achieved by boss or rib type depressions 4'.

In all embodiments as described the heat sensor 6 disposed within the tube sleeve 4, 13 and within channel 17", respectively, due to the good heat transfer conditions assumes a temperature being above the temperature of the water under normal operating conditions. Upon temporary switch-off or reduction of the heating capacity, the

temperature of the heat sensor 6 drops only relatively little as the temperature of the water continues to exercise a strong influence on the temperature of the heat sensor. By the influence of the fin block temperature on the temperature of the heat sensor 6 a resp nse of the thermostat is ensured in the case of water deficiency or formation of vapor. If an additional thermostat of the central heating system, connected between the heat exchanger and the radiator of the heating system, controlling the water temperature fails to operate, then the safety thermostat c ntrolled by the heat sensor 6 due to a sufficient water temerature influence will also respond to an intolerable increase in the water temperature so that a control of the thermostat disposed bet-ween the heat exchanger and the radiator of the heating system is thus achieved. It is of importance that the heat sensor t5 engages that portion of sleeve 4, 13 and of channel 17, respectively, that is disposed to the side of the water.

Assuming that the temperature limiting device in a closed heating system of a hot-water heating system shall switch ofi at a temperature between heat exchanger and radiator of the heating system of 230 F., the heat sensor 6 which is additionally influenced by the higher temperature of the fin block and the fin tube, respectively, must reach a switch-off temperature of 262.4 F. If the continuous-fiow heater is temporarily run with strongly reduced capacity, for instance half, the temperature of the fin tube Will decrease more strongly than that of the water. The heat sensor will now receive less heat from the side of the fin tube. Therefore, the heat sensor will only reach the switch-off temperature of 262.4 F. at a higher water temperature than was previously provided with 230 F. If the heat sensor 6 engaged the bottom of sleeve 4 and 13, respectively, in an unfavorable manner, the water temperature, as has been determined by measurements increases up to 251.6 F., before the heat sensor 6 reaches its switch-off temperature of 262.4 F. This means that switch-off by the temperature limiting device instead of at 230 F., will only take place at a 2l.6 F. higher temperature between the heat exchanger and the radiator of the heating system of 251.6 F. If, however, the heat sensor-as has been described hereiribefore-abuts at the top, that is at the side of sleeve 4 and 13, respectively, facing the water, it will already reach its switch-off temperature of 262.4 F. at a water temperature of from 237.2 to 239 F. so that thus at half heating capacity only an excess temperature of 9 F. insteadof 21.6 F. must be put up with.

The invention is claimed as follows:

1. In the mounting of a temperature sensor in a hot Water heating system having a fin block through which water flows and externally of which the hot gases of combustion flow, the improvement comprising: metallic means defining a well enclosed except for one end and receiving said sensor, said means having a first portion of its external area exposed to said water and a second portion of its external area exposed to said gases with direct metal heat conduction paths between said areas and said well, said first portion being a major part of the eX- posed area of said means, and said second portion being a substantial part of said exposed area whereby said sensor is strongly influenced by the temperatures f both the Water and the hot gases.

2. In a mounting as set forth in claim 1, including means urging said sensor into contact the part of the metallic means most closely adjacent said first portion.

3. In a mounting as set forth in claim 2, wherein said metallic means includes a fin tube of said fin block, a sleeve and a soldered connection therebetween, said sleeve having closed and open ends and being positioned in the tube with its closed end in the tube and its open end outside said tube, said sleeve being positioned against an inner side of the tube and soldered thereto.

4. In a mounting as set forth in claim 2, wherein said metallic means includes a fin tube of said fin block, a sleeve and a soldered connection therebetween, said sleeve having closed and Open ends and being positioned externally of the tube in contact therewith and soldered thereto.

5. In a mounting as set forth in claim 2, wherein said metallic means includes a unitary fin tube carrying the water with a 'well along one side of the outside thereof.

6. In a mounting as set forth in claim 1, wherein said metallic means includes a fin tube of said fin block, a sleeve and a soldered connection therebetween, said sleeve having closed and open ends and being positioned in the tube with its closed end in the tube and its open end outside said tube, said sleeve being positioned against an inner side of the tube and soldered thereto.

7. In a mounting as set forth in claim 6, wherein said metallic means includes a fluid guiding plate extending longitudinally and radially of said tube with one side thereof fitting about the sides of the sleeve in contact therewith.

8. In a mounting as set forth in claim 1, wherein aid metallic means includes a fin tube of said in block, a sleeve and a soldered connection therebetween, said sleeve having closed and open ends and being positioned externally of the tube in contact therewith and soldered thereto.

9. In a mounting as set forth in claim 1, wherein said metallic means includes a unitary fin tube carrying the water with a well along one side of the outside thereof.

References Cited UNITED STATES PATENTS 2,047,223 7/ 1936 Prickett 73349 2,197,582 4/1940 Kaufman 73368 3,266,3'18 8/1966 Abajian et 'al. 73368 1,886,042 11/1932 Osborne 73-362.8 2,266,321 12/1941 Holder 236-99 LOUIS R. PRINCE, Primary Examiner.

N. B. SIEGEL, Assistant Examiner. 

